The Health Behavior in School-aged Children (HBSC) study is a cross-national research survey conducted in collaboration with the World Health Organization (WHO) Regional Office for Europe. HBSC aims to gain new insight into, and increase our understanding of young peoples health and well-being, health behaviors and their social context. Initiated in 1982 in three countries, there are now over 40 participating countries and regions. The first cross-national survey was conducted in 1983/84, the second in 1985/86, and subsequently every four years using a common research protocol. The U.S. has been associated with the HBSC since 1993/94 and a fully participating member since 1997/98. Studies using the 2001/02 data have examined associations between bullying and family, peer, and school relations for White, Black and Hispanic adolescents. Parental communication, social isolation, and classmate relationships were similarly related to bullying across racial/ethnic groups. Living with two biological parents was protective against bullying involvement for White students only. Further, although school satisfaction and performance were negatively associated with bullying involvement for White and Hispanic students, school factors were largely unrelated to bullying among Black students. Obesity has also been a focus of work with the 2001/02 data. For example, the association of timing of pubertal maturation with the increased body size of U.S. adolescents has been examined. In girls particularly, early maturation is associated with a higher BMI and overweight. Since other maturational patterns, especially risk-taking behavior, may also be associated with pubertal development, this relationship was investigated in the U.S. HBSC. Examples of risk behaviors examined included whether the adolescent had ever smoked tobacco or drunk alcohol to excess (got drunk). Boys pubertal status was indicated by the appearance of hair on the upper lip (around Tanner pubic hair stage 4) and girls by menarche (between Tanner pubic hair stages 3 and 4). At every age during peak pubertal periods, more mature adolescents were significantly taller and heavier, and the reported frequency of risk behaviors increased with age and maturational status. Adjusting for age, ethnic differences, residence and perception of family affluence, more mature boys with facial hair and post-menarcheal girls were almost twice as likely to have ever smoked or reported getting drunk. Thus, not only is the timing of pubertal maturation a factor in the development of adolescent overweight, but also in the development of risk behaviors. We also examined the relationship of youth cigarette smoking status to state-level youth access and clean indoor-air laws, controlling for socio-demographic characteristics and cigarette price. Compared to students living in states with strict regulations, those living in states with no or minimal restrictions, particularly high school students, were more likely to be daily smokers. The most recent survey was just completed for 2005/06. Besides contributing to the international survey, the U.S. simultaneously mounts a nationally representative school-based survey of approximately 10,000 students in grades 6 to 10 using identical data collection methods. Recent major studies from the 2005/06 survey have focused on the prevalence, patterns, determinants, and effects of violence and bullying behaviors, the epidemiology of substance use among young adolescents, the causes and consequences of physical inactivity, and the effect of public policy. A strength of the HBSC is the ability to make cross-country comparisons. With respect to bullying, involvement in bullying varied dramatically across countries, ranging from 10-67%, and was associated with poorer psychosocial adjustment. Trend analyses indicated that the U.S. was the only English-speaking country with a decrease in bullying involvement over the last 8 years. In all or nearly all countries, bullies, victims, and bully-victims reported greater health problems and poorer emotional and social adjustment. Victims and bully-victims consistently reported poorer relationships with classmates, while bullies and bully-victims reported greater alcohol use and weapon-carrying. With respect so substance use, the prevalence of adolescent drinking and drunkenness (except among Dutch girls) was generally lower in the United States, where strict drinking policies are in place, than in Canada and the Netherlands, where harm reduction policies are in place. However, the only difference in marijuana use rates was lower use by Dutch, a finding that is not consistent with the contention that prohibition-oriented policies deter use. Rates of student physical aggression were compared between Canada and the U.S. School, family, socioeconomic, and peer-related factors were considered as potential risk factors. A simple social environment risk score was developed using the US data and was subsequently tested in the Canadian sample. Risks for physical aggression were consistently higher among US vs. Canadian students, but the magnitude of these differences was modest. The relative odds of physical aggression increased with reported environmental risk. Electronic forms of bullying (e.g., email, cell-phone) were added to the 2005/06 survey. Prevalence rates of having bullied others or having been bullied at school for at least once in the last 2 months were 20.8% physically, 53.6% verbally, 51.4% socially or 13.6% electronically. Boys were more involved in physical or verbal bullying, while girls were more involved in relational bullying. Boys were more likely to be electronic bullies, while girls were more likely to be electronic victims. African-American adolescents were involved in more bullying (physical, verbal or electronic) but less victimization (verbal or relational). Higher parental support was associated with less involvement across all forms and classifications of bullying/victimization. Having more friends was associated with more bullying and less victimization for physical, verbal and relational forms, but was not associated with electronic bullying/victimization. With regard to risk factors for obesity, self-reported psychological and social health indices such as self-image, perceived health status, and quality of life were positively related to physical activity in representative countries from all international regions but, with a few exceptions, negatively related to screen-based sedentary behavior. Regional differences in correlates of physical activity and screen-based sedentary behavior suggest cultural differences in potential effects of physical activity and screen-based sedentary behavior and the need to tailor school and public health efforts to the different meanings of physical activity and screen-based sedentary behavior for positive and negative health consequences.